1. Field of the Invention
The invention relates to power supplies, and more particularly to an uninterruptible power supply which supplies clean and continuous electrical power to a load.
2. Description of the Prior Art
A variety of power supplies exist for powering various electronic devices. A large number of the electronic devices require continuous power for proper operation. For example, computers must receive continuous power in order to avoid costly down time, and more importantly, prevent the loss of data. Therefore, unforseeable power source line disturbances, ranging from deviations from the specified line voltage known as "Brown-outs" or "Brown-power" to complete loss of power, must be eliminated to provide the desired continuous power to the electronic device or computer.
Conventional uninterruptible power supplies traditionally condition the AC line voltage from the power source line to provide useable continuous power. In particular, high power 60 Hz transformers have been utilized to provide isolation from the power source line. While the high power 60 Hz transformers provide isolation from the power source line, the 60 Hz transformers have excessive weight and may interfere with common applications which involve computers and computer networks.
Conventional uninterruptible power supplies typically utilize an array of on-board storage devices or batteries to supply reserve power when there is a line disturbance or power shortage on the power source line. These storage devices may only provide adequate power for a short period of time before they need to be recharged. Therefore, an immediate switch from power source line power to reserve power from the batteries when the power source line voltage sags below a first threshold value may result in the premature depletion of battery power.